It is a common practice to install ventilators in openings in building walls, such as foundation walls, to provide for the flow of ventilating air through the enclosed crawl space beneath the floor of the building. Normally, the foundation ventilators are installed in the wall openings by applying mortar around the outer edges of the ventilator when it is positioned in the opening.
Commonly owned U.S. Pat. No. 4,274,330 discloses a ventilator mounting frame assembly in which a rectangular frame is first mounted in the opening by means of adjustable fasteners which engage the interior surface adjacent the opening and are adjustable by elongated screws carried by the mounting frame for maintaining the mounting frame in position in the opening. The ventilator is then positioned in and fixed to the mounting frame. The mounting of the ventilator in accordance with this patent requires that the mounting frame and the ventilator be formed in two separate parts and that the mounting frame be initially installed and then the ventilator installed in the mounting frame, which adds to the cost of manufacturing and complicates the installing procedure.
U.S. Pat. No. 3,220,079 discloses a foundation ventilator which is easily and simply mounted in a concrete foundation wall by pushing the same into engagement with resilient flanges on a metal vent box which is positioned in the wall and the concrete is poured around the vent box to provide the wall opening in which the foundation ventilator is supported. However, the foundation ventilator disclosed in this patent is not adapted for mounting in a foundation wall formed of brick and the manufacture and positioning of the vent support box in the foundation adds to the cost of manufacture and installation of the ventilators.
Recently it has been the common practice to form the mounting frame of the foundation ventilator of molded plastic material and to support the ventilator in the wall opening by screws threadably supported in opposite sides of the mounting frame. The mounting frame is positioned in the wall opening and the screws are adjusted outwardly until their outer ends firmly engage the opposite side portions of the wall opening. However, the plastic mounting frame expands when the temperature rises and contracts when the temperature drops so that the screws are not maintained in the proper amount of firm engagement with the wall opening under all temperature conditions. If the ventilator is installed when the temperature is high, the screws tend to loosen when the temperature drops and the mounting frame contracts so that the ventilator may fall out of the wall opening. If the ventilator is installed when the temperature is low, the screws become tighter when the temperature rises and the mounting frame expands so that the mounting frame may be bowed outwardly from the wall opening.